Propeller



Aug. 9, 1960 w T 2,948,254

PROPELLER Filed Aug. 12, 1959 INVENTQR.

Geonye fl. W177.

\ PR ELL R. George A. p 7 6,

F Ali t g g T 2 Claims. (21. 115- 17) This invention relates to propellers such as used in connection with power plants of boats and more particularly to propellers used on speed boats and with either in-board or out-board motors.

One of the prime objects of the invention is to design a propeller comprising concentrically arranged inner and outer sleeves having blades thereon, the blades on the inner sleeve being of less pitch than the pitch on the outer blades, thus providing smoother, straight-ahead starting torque to start and force acceleration of the boat through the water, after which the blades of the outer sleeve will provide increased driving torque to drive the boat at higher speeds.

Another object of the invention is to design a propeller of simple, practical and economical construction, which provides for fast, smooth get-away when the boat is started, as well as eificient propulsion of the boat at high speeds because of minimum displacement due to water resistance.

A further object is to provide a propeller which can j be readily mounted on the drive shaft of a power plant' and which requires no change in the shaft or conventional method of mounting.

Still a further object is to provide a unitary twin propeller mechanism, one of which is extremely eflicient and stable to start and propel the boat at lowpropulsion speeds, while the other is most efficient at high propulsion speeds. 1

A further object still is to design a unitary propeller comprising inner and outer blades concentrically arranged with relation to each other.

With the above and other objects in view, the present invention consists in the combination and arrangement of parts, hereinafter more fully described, illustrated in the accompanying drawing, and more particularly pointed out in the appended claims, it being understood,

that changes may be made in the form, size, proportion, and minor details of construction, without departing from the spirit, or sacrificing any of the advantages of the invention.

In the drawing: h

Fig. 1 is a side elevational view of an outboard motor showing my improved twin propeller in place on the propeller shaft thereof.

Fig. 2 is an enlarged, sectional, elevational view of the propeller.

Fig. 3 is a side elevational view thereof.

Fig. 4 is a view similar to Fig. 2. showing a slightly modified design.

Fig. 5 is a view taken on line 55 of Fig. 1.

Referring now more particularly to the drawing in app ve mahher, niese propeller ,sectians anas eeve's being gange cally arra ges war relates to each'oth'e'r' vjn r ra p mps dbehereiaartr mo fur -assented. "w r. lad s. 1 ar si i hi' slaw; 11;. iythe mh'ge er from '10? to 3o 51 t 1i, {so that when s it fore cast an outer sleeve 13 on the blades 12, and the propeller blades 14 are secured on the outer face of said sleeve and normally extend the full length thereof, as indicated in Figures 1 and 3 of the drawing, these blades having a. very high pitch in the range of from 20 to 80 pitch, this high pitch being best adapted, after the boat has been brought up to speed, to drive the boat at very high speeds on the theory that a high pitch at high speeds presents less water resistance with maximum driving torque.

I wish to direct particular attention to the fact that the front end of the propeller sleeves are spaced from the skeg portion S of the motor which includes an upper leg portion 15, a dependent portion 16, and an intermediate annular bearing portion 17 of substantially the outer diameter of sleeve 13 which supports shaft 10. Accordingly, water readily'enters the sleeve 11 at low speeds from in back of bearing 17, and this sleeve terminates short of the rear end of the sleeve 13, insuring that the blades 14 will operate in water which has not been unduly agitated so that maximum driving power is obtained.

At high speeds a void formed behind the skeg as the acceleration and also for eificient propulsion at high speeds with a minimum displacement of the water.

What I claim is: r

1. In combination, an outboard motor including a depending skeg and a horizontal drive shaft supported a considerable distance above the lowerend of the skeg,v

a propeller fixed on said drive shaft a spaced distance rearward of the skeg comprising an inner sleeve fitting on said shaft and an outermost sleeve concentric with said inner sleeve a spaced distance radially outward thereof, circumferentially spaced, outer, helical blades of relatively high pitch secured at their inner ends to said outermost sleeve with their outer ends free to contact water from all directions, circumferentially spaced, helical, inner blades of substantially lower pitch than said outer blades secured at their inner and outer ends to the inner and outermost sleeves respectively with the said skeg extending beyond said inner blades so that at high speeds an air pocket is formed behind the skegand no water reaches the inner blades so that the outer blades of high pitch solely drive through the water at high speeds, said which I have shown the preferred embodiment of my invention the letter '0 indicates a conventional out-board motor such as used to power small boats in general.

This is provided with a horizontally disposed drive shaft 10 on which the propeller P is' mounted, said propeller comprising inner and outer tubular sleeves, 11 and 13 on which blades 12 and 14 are cast or secured in any' difierent pitches of the inner and outer blades being such that at lowstarting speeds the inner blades drive through the water while at high speeds no water reaches the inner sleeve behind, the skeg and theouter blades drive through considerable distance above the lower end of the skeg,

a propeller fixed on said drive shaft a spaced distance rearward of the skeg comprising an inner sleeve fitting on said shaft and an outermost sleeve concentric with said inner sleeve supported a spaced distance radially outward thereof, circumferentially spaced, outer, helical blades of relatively high pitch secured at their inner ends tosaid outermost sleeve with their outer ends free to contact water circumferentially from all directions, circumferentially spaced, helical, inner blades of substantially lower pitch than said outer blades secured at their inner and outer ends to the inner and outer sleeves respectively with the skeg extending beyond said inner blades so that at high speeds an air pocket is formed behind the skeg and no water reaches the inner blades .50 that the outer blades of high pitch solely drive through 15 4, the water at high speeds, said difierent pitches of the inner and outer blades being such that at, low starting speeds the inner blades drive through the Water while at high speeds no water reachesthe inner sleeve behind the skeg and the outer blades drive through the water and exert the thrust, the inner sleeve and blades thereon being spaced at least no further rearward from the skeg than the outer sleeve and blades thereon so that the blades on the outermost sleeve do not interfere with the oper- 10 ation of the inner blades at-low speeds.

References Citedin the file of this patent h UNITED'STATES PATENTS 130,391 Shepard Aug. 13, 1872 

